Cathode ray tube gun assembly



April 9, 1963 w. 0. SMITH CATHODE RAY TUBE GUN ASSEMBLY Filed March 11.1959 zoi INVENTOR. Men 0544 0. 6M/ 71/ United States Patent 3,%5,l72CATHUDE RAY TUBE GUN ASElEWBLY Wendell 0. Smith, Corning, NY assign-orto Qorning Glass Worlrs, Qorning, N511, a corporation of New York FiledMar. 11, 1959, 3am No. 793,724? 2 tilaims. (6i. 313-32) The presentinvention relates to cathode ray tubes and more particularly to animprovement in the electron gun structures therefor.

Although many different electrode configurations have been devisedheretofore to provide electrostatic focusing for the electron beams incathode ray or other charged particle tubes, the various elements of theguns thereof have customarily been made structurally unitary by means oflongitudinally plane surfaced insulating rods, com posed of glass or thelike, extending along two opposite sides of the assembled and properlyspaced electrodes attached thereto by means of studs projecting fromsuch electrodes into the rods.

In the continuing effort to improve the efhciency of such guns theirdimensions and the diameter of the tube necks enclosing them have beenreduced from time to time.

Since in use of the tube, at least one of the gun elements is at highvoltage potential while others are at ground or relatively lowpotential, a substantial number of such guns fail because of highvoltage leakage and arcing along the relatively short paths along theirrod surfaces.

In the older electron guns the enclosing tubes were of relatively largediameter and length compared to present day requirements. This permitteda liberal spacing of the respective gun elements with respect to oneanother along their supporting rods and, accordingly, gun failure fromsuch causes as improper spacing of the respective elements from oneanother, surface contamination of the rods, or from the use of excessivetest voltages rarely resulted.

ln the modern electron guns the enclosing tubes have been materiallyreduced both in diameter and length, thus making it necessary to reducethe size and spacing of the gun elements and of their support rods tosuch an extent that failure from one or another of the foregoing causesfrequently occurs.

One known structure, devised with a view to reduce tube failures fromthe foregoing causes, supports those electrodes at or near groundpotential between one pair of such rods and those at high andintermediate potentials between a second pair of such rods radiallyremoved from the first pair 90. Such a structural arrangement, whilehelpful, is complicated by the use of four rather than but two electrodesupport rods.

According to the invention rods having plain surfaces are replaced withrods shaped or surface figured to impart to them a greatly increasedsurface length, as by giving them a surface that is non-planar parallelto their longitudinal axes, thus giving them surface resistancestherealong comparable to and even greater than those employed in thehereinbefore referred to older types of guns. Such a structure greatlyreduces the danger of gun failure resulting from high voltage leakageand arcing along the rod surfaces without complicating it by use of twopairs of rods, but nevertheless is equally applicable to the latter formof structure to further improve it.

For a better understanding of the invention reference will hereinafterbe made to the accompanying drawing wherein:

FIG. 1 is an enlarged vertical elevation of an electron gun constructedaccording to the invention and having the tube envelope broken away.

FIG. 2 is a greatly enlarged vertical elevation of gun electrodeassembly sectioned to the right of centerline.

Referring in detail to the drawing, there is illustrated the neck 2 andbase i of a cathode ray tube, the enlarged bulb and screen supportingface of which are not shown. Supported within the neck 2 is an electrongun of the type commonly known as a straight gun. This electron guncomprises a cathode grid assembly 6, a second grid 3, an anode it}, afocusing ring 12 and an accel rating anode 14.

The respective gun elements 6, 3, 1d, 12, and 14 are made structurallyunitary by spot welding to two opposite sides of each of such elementsthe closed ends of U-shaped studs, such as 2% and 22, and by embeddingtheir free ends into rods 24 and '25 of dielectric material, such asglass or the like.

According to the invention the rods 24 and 2-5, instead of, as inconventional past practice, having their exterior surfaces extending inplanes parallel to their longitudinal axes, are provided along theirlengths with undulating or transversely ribbed surfaces 353-, therebygreatly elongating their surface length. Such rods, accordingly, havesurface resistances between the respective gun elements comparable to orgreater than those employed in the older forms of electron guns.

Obviously, the character of configuration given to the rods to suitablyincrease the leakage paths between the respective electrode elements maytake any of a great variety of forms without departing from the spiritof the invention.

What is claimed is:

1. An electron gun comprising a cathode element for emitting electronsalong an electron beam path, an electron creating and focusing structurecomprising in order along said beam from said cathode element, a firstgrid element, a second grid element, an anode element, a focusingelectrode element, and an accelerating anode element arranged in theorder named, and two rods of dielectric material rigidly supportnig saidelements therebetween along their length in predetermined juxtaposedspaced relation with respect to one another, said rods being of a lengthwhich is substantially no greater than the distance between the regionsof their connections with the first grid element and with theaccelerating element respectively having surfaces figured to affordmaximum leakage paths over their surfaces between respec tive ones ofsaid elements.

2. in an electron gun providing electrostatic focusing for the electronbeams in cathode ray and other charged particle tubes having a pluralityof gun elements made substantially unitary by being rigidly supported insuitably spaced relation between rods of rigid dielectric material, theimprovement which comprises use of rods straight throughout theirlengths having surfaces that are non-planar parallel to their axes toincrease the length of the surface paths between points of attachment ofthe respective elements thereto.

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References (fed in the file of this patent UNITED STATES PATENTS2,460,201 Trump Jan. 25, 1949 2,578,908 Turner Dec. 18, 1951 2,810,851Johnson Oct. 22, 1957 2,836,788 Atlee May 27, 1958 2,927,233 BarnettMar. 1, 1960 FOREIGN PATENTS 740,263 Great Britain Nov. 9, 1955

1. AN ELECTRON GUN COMPRISING A CATHODE ELEMENT FOR EMITTING ELECTRONSALONG AN ELECTRON BEAM PATH, AN ELECTRON CREATING AND FOCUSING STRUCTURECOMPRISING IN ORDER ALONG SAID BEAM FROM SAID CATHODE ELEMENT, A FIRSTGRID ELEMENT, A SECOND GRID ELEMENT, AN ANODE ELEMENT, A FOCUSINGELECTRODE ELEMENT, AND AN ACCELERATING ANODE ELEMENT ARRANGED IN THEORDER NAMED, AND TWO RODS OF DIELECTRIC MATERIAL RIGIDLY SUPPORTING SAIDELEMENTS THEREBETWEEN ALONG THEIR LENGTH IN PREDETERMINED JUXTAPOSEDSPACED RELATION WITH RESPECT TO ONE ANOTHER, SAID RODS BEING OF A LENGTHWHICH IS SUBSTANTIALLY NO GREATER THAN THE DISTANCE BETWEEN THE REGIONSOF THEIR CONNECTIONS WITH THE FIRST GRID ELEMENT AND WITH THEACCELERATING ELEMENT RESPECTIVELY HAVING SURFACES FIGURED TO AFFORDMAXI-